1. Field of the Invention
This invention relates generally to the field of multimedia systems. More particularly, the invention relates to a multimedia system capable of selecting between different network protocols for transmitting and receiving data and multimedia content.
2. Description of the Related Art
A prior art system for receiving a digital multimedia signal is illustrated in FIG. 1a. As illustrated, one or more tuners 120, 121 are configured to lock on to video signals 100, 101 transmitted at a carrier frequency and down-convert the signals to baseband. Quadrature Amplitude Modulation (xe2x80x9cQAMxe2x80x9d) demodulators 130, 131 demodulate the baseband signals to extract the underlying digital data. As is known in the art, QAM is a modulation technique employed by cable and satellite providers that generates four bits out of one baud. For example, a 600 baud line (600 shifts in the signal per second) can effectively transmit 2,400 bps using this method. Both phase and amplitude are shaped with each baud, resulting in four possible patterns.
The demodulated signal is then transmitted to conditional access (xe2x80x9cCAxe2x80x9d) subsystems 140, 141 which prevent channels/content from being transmitted on the system which the user does not have the right to receive (e.g., subscription-based content such as HBO or pay-per-view channels). CA subsystems 140, 141 are well known in the art and are currently manufactured by only a small group of companies including Scientific Atlanta,(trademark) Motorola,(trademark) General Instrument(trademark) and DVB(trademark).
If the CA subsystem 140, 141 allows the user to view a particular channel then multimedia content (i.e., audio and/or video content) from the channel is transmitted over a system bus 151 (via bus interface 150) to a mass storage device 160. An MPEG-2 decoder module 170 coupled to the system bus 151 decodes/decompresses the multimedia content before it is rendered on a multimedia rendering device 135 (e.g., a television).
Prior art systems may also utilize a main memory 126 for storing instructions and data and a central processing unit (xe2x80x9cPUxe2x80x9d) 125 for executing the instructions and data. For example, the CPU may provide a graphical user interface displayed on the television, allowing the user to select certain television or audio programs for playback and/or storage on the mass storage device 120.
The system illustrated in FIG. 1a is capable of concurrently receiving, decoding and storing multimedia content from two independent broadcast channels (i.e., via tuners 120 and 121). One limitation of this system, however, is that it does not provide a return channel for two-way communication. As such, users are unable to transmit data back to the cable or satellite provider or otherwise interact with the multimedia content.
To address these limitations, the prior art system illustrated in FIG. 1b includes a separate modem unit 190 comprised of a tuner 122 for receiving data, a QAM module 132, and a transmitter/modulator unit 190 for transmitting data over a network (e.g., the Internet). As indicated in FIG. 1b, the QAM module 132 is configured to support the Data Over Cable Service Interface Specification (xe2x80x9cDOCSISxe2x80x9d), a set of accepted standards for transferring packetized data over cable TV networks. Thus, using the system of FIG. 1b, a user is able to concurrently receive two cable broadcast channels while communicating over the Internet (e.g., sending email, browsing Web pages, downloading interactive content related to a particular TV program, . . . etc).
While the modem unit 190 provides the benefit of two-way communication, it also generates a significant additional cost as a result of the third system tuner 122, third QAM module 132, third CA subsystem 142 and the transmitter/modulator unit 190. Moreover, because the legacy systems shown in FIGS. 1a-b rely on proprietary technology (such as CA subsystems developed by third parties), cable providers are limited in their ability to modify the underlying protocols used to transmit multimedia content to the end user. As such, new transmission techniques/protocols which would allow cable providers to transmit content in a more flexible, efficient and intelligent manner may not be employed. For example, using a packet-switched protocol such as DOCSIS to transmit and receive multimedia content (as well as data), cable operators would be able to dynamically route content to end users more efficiently and would have the flexibility to implement their own security mechanisms (e.g., those used for secure communication over the Internet).
Accordingly, what is needed is a system and method for receiving and transmitting data and multimedia content over a cable network in a more flexible, efficient and intelligent manner. What is also needed is a system which is backwards-compatible with currently-existing network protocols and standards and which is less costly to manufacture than current systems, while providing at least the same level of functionality as current systems.
A multimedia apparatus is described comprising: a tuner for tuning to a carrier frequency and down-converting a frequency-modulated multimedia signal to a baseband multimedia signal; a selectable protocol module including QAM/MPEG logic and Data Over Cable Service Interface Specification (xe2x80x9cDOCSISxe2x80x9d) logic configured to receive the baseband multimedia signal; and selection logic configured to select the QAM/MPEG logic for processing a first signal having a first signal format to produce a first processed signal, the selection logic further configured to select the DOCSIS logic for processing a second signal having a second signal format to produce a second processed signal.
Also described is a multimedia communication system comprising: a communication channel configured to switch between a first mode in which the communication channel receives and decodes a first multimedia signal using MPEG logic, and a second mode in which the communication channel transmits and receives data and/or multimedia content according to the Data Over Cable Service Interface Specification (xe2x80x9cDOCSISxe2x80x9d) standard.
Also described is a method implemented by a multimedia service provider for transitioning to a Data Over Cable Service Interface Specification (xe2x80x9cDOCSISxe2x80x9d) communication standard comprising: providing subscribers with a first type of multimedia system having one or more selectable protocol modules, the selectable protocol modules being capable of selecting between a legacy communication standard and a DOCSIS communication standard for transmitting/receiving data and/or multimedia content; and switching from the legacy communication standard to a DOCSIS-only communication standard to transmit/receive multimedia content and/or data; and
providing new subscribers with a second type of multimedia system having one or more DOCSIS modules capable of transmitting/receiving data and/or multimedia content according to the DOCSIS standard.